Presently, screw driver bits for use with power screw drivers are normally designed with a hexagonal rear end to permit an easily removable insertion into a mating internally hexagonal drive socket in the power screw driver. It may then sometimes happen that the screw driver bit after extensive use may become jammed within the drive socket under a wedging action due to a deformation by swaging.
In connection with nut tightening apparatuses of the impact type it has been proposed to design the drive mechanism in such a manner that the blows hit the rotary socket pin simultaneously on both sides thereof.
The U.S. Pat. No. 2,564,356, to A. E. Dianda, discloses a screw driver the handle of which comprises two parts. The foremost part is rigidly secured to the screw driver bit, whereas the rearmost part is rotatable with respect to the foremost part and is connected to the bit stem by means of a latch coupling. The latch coupling comprises a plurality of latch teeth at the rear end of the bit stem and a spring biased lath in the rearmost handle portion for engagement with said latch teeth. Such an arrangement may be entirely satisfying for a mannual screw driver but is far too weak for a power screw driver.